“ We believe that the District Court should have stayed its hand. The power of the judiciary of a State to require valid reapportionment or to formulate a valid redistricting plan has not only been recognized by this Court but appropriate action by the States in such cases has been specifically encouraged. ”

“ The District Court shall retain jurisdiction of the case and in the event a valid reapportionment plan for the State Senate is not timely adopted it may enter such orders an it deems appropriate, including an order for a valid reapportionment plan for the State Senate or an order directing that its members be elected at large pending a valid reapportionment by the State itself. ”

“ It further held that if no such 'implementation, amendment or substitution' was submitted it would order the parties to show cause why all Illinois State Senators should not be elected from the State at large in the 1966 election and every four years thereafter. ”